In the field of LED drivers for offline application, solutions are demanded to achieve, inter alia, high efficiency, high power density, long life time, high power factor or low cost. The LED units known from the prior art are usually designed to be connected to a DC-voltage supply. An LED unit including a driver circuit designed to be connectable to a DC-voltage supply is e.g. known from JP 5136461A. Practically, the LEDs and the driver circuits should be designed to be connectable to the mains input and should transform the mains energy into the form required by the LEDs while keeping compliance with present and future power mains regulations. It is of critical importance to guarantee a high efficiency of the LEDs even if the supply voltage of the mains input is a voltage having a variation of up to ±10%.
Usually, a rectifier bridge is used to connect the LEDs to the mains input to provide a DC voltage, which is necessary to drive the LED unit. The rectified voltage usually still comprises an AC component and the efficiency normally decreases considerably in the case of variations of the input voltage.
Further, it is known in the field of LEDs to modulate the light output of a lamp and to embed information into the light in a way not visible to the user. This modulated light can send data to a receiver located beneath or in the proximity of the respective lamp. A method of modulating light signals is described in detail in WO 2009/010909.
The driving circuits to modulate the light output are usually complex and include a large amount of components.